/*
 * Alloy Analyzer 4 -- Copyright (c) 2006-2008, Felix Chang
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package edu.mit.csail.sdg.alloy4viz;

import java.util.Collection;
import java.util.Collections;
import java.util.ArrayList;
import java.util.List;
import edu.mit.csail.sdg.alloy4.Util;

/**
 * Immutable; represents an Alloy tuple.
 *
 * <p><b>Thread Safety:</b> Can be called only by the AWT event thread.
 */

public final class AlloyTuple implements Comparable<AlloyTuple> {

    /** The unmodifiable list of atoms in this tuple. */
    private final List<AlloyAtom> atoms;

    /** Creates a new AlloyTuple containing the atoms specified by the list; atoms.size() must be 2 or above. */
    public AlloyTuple(List<AlloyAtom> atoms) {
        if (atoms==null || atoms.size()<2)
            throw new RuntimeException("An AlloyTuple object must have 2 or more atoms.");
        this.atoms = Collections.unmodifiableList(new ArrayList<AlloyAtom>(atoms));
    }

    /** Creates a new AlloyTuple containing the atoms specified by the list; atoms.size() must be 2 or above. */
    public AlloyTuple(AlloyAtom... atoms) {
        if (atoms==null || atoms.length<2)
            throw new RuntimeException("An AlloyTuple object must have 2 or more atoms.");
        this.atoms = Util.asList(atoms);
    }

    /**
     * Project this tuple and return an unmodifiable list of remaining atoms (after removing zero or more columns)
     * @param columns - the collection of columns to remove (0 is the first column, 1 is the second column...)
     */
    public List<AlloyAtom> project(Collection<Integer> columns) {
        List<AlloyAtom> list=new ArrayList<AlloyAtom>(atoms.size());
        for(int i=0; i<atoms.size(); i++) if (!columns.contains(i)) list.add(atoms.get(i));
        if (list.size()==atoms.size()) return this.atoms; else return Collections.unmodifiableList(list);
    }

    /** Returns the arity of this AlloyTuple. */
    public int getArity() { return atoms.size(); }

    /** Returns an unmodifiable list of the AlloyAtoms in this AlloyTuple. */
    public List<AlloyAtom> getAtoms() { return atoms; }

    /** Returns the first AlloyAtom in this AlloyTuple. */
    public AlloyAtom getStart() { return atoms.get(0); }

    /** Returns the last AlloyAtom in this AlloyTuple. */
    public AlloyAtom getEnd() { return atoms.get(atoms.size()-1); }

    /** Returns a new AlloyTuple whose list of atoms is the same but in reverse. */
    public AlloyTuple reversed() {
        List<AlloyAtom> newlist = new ArrayList<AlloyAtom>(atoms.size());
        for(int i=atoms.size()-1; i>=0; i--) newlist.add(atoms.get(i));
        return new AlloyTuple(newlist);
    }

    /** Provides a human-readable description of this AlloyTuple. */
    @Override public String toString() {
        String s="<";
        for(int i=0; i<atoms.size(); i++) { if (i!=0) s=s+", "; s=s+atoms.get(i); }
        return s+">";
    }

    /**
     * Two tuples are first compared based on length; if the length is the same, we compare atom-by-atom.
     * <br> We guarantee x.equals(y) iff x.compareTo(y)==0
     */
    public int compareTo(AlloyTuple that) {
        if (that==null) return 1;
        if (atoms.size() < that.atoms.size()) return -1;
        if (atoms.size() > that.atoms.size()) return 1;
        for(int i=0; i<atoms.size(); i++) {
            int result=atoms.get(i).compareTo(that.atoms.get(i));
            if (result!=0) return result;
        }
        return 0;
    }

    /** Two tuples are equal if they have the same atoms in the same order. */
    @Override public boolean equals(Object other) {
        if (!(other instanceof AlloyTuple)) return false;
        if (other==this) return true;
        return atoms.equals(((AlloyTuple)other).atoms);
    }

    /** Compute a hash code based on the list of atoms. */
    @Override public int hashCode() { return atoms.hashCode(); }
}
